Yesterday, for some reason, the Google Search Console AMP (Accelerated Mobile Pages) report under the Search Appearance section, shows a huge spike in both indexed pages and errors. The next day, the report dropped back down to normal compared to the rest of the time frame.
Here is a screen shot from one of my sites:
The spike reached over 15,000 indexed AMP URLs and 143 errors, which was about double the average for the rest of the time frame in this report.
â” Eugene Feygin (@rawseo) March 2, 2017
Google has not commented yet on the issue but it must have been a weird reporting glitch that double counted the data on March 1, 2017.